This grant supports studies on factors regulating renal electrolyte excretion. Balance techniques are used to evaluate the role of reninangiotensin-aldosterone system in health and disease with particular emphasis on the changes in response pattern of the renin- angiotensin- aldosterone system to variations in sodium intake in hypertension. Radioimmunoassay of Angiotensin II and Aldosterone are used in evaluating hormonal responses in these patients. Studies in the renin- angiotensin- aldosterone system as the major regulator of sodium metabolism are proposed that should increase understanding of the mechanisms that operate to control the level of circulating Angiotensin II. The proposed studies include monitoring of the renin-angiotensin- aldosterone system during balance studies as described above as well as measuring the transpulmonary generation of angiotensin II in patients undergoing cardiac catheterization for diagnostic purposes. These studies will provide information to decide whether renin release is the primary determinant of angiotensin II in the plasma/whether other factors in the reaction sequence are of more importance. Other factors responsible for controlling aldosterone output in the absence of the renin-angiotensin system are to be studied in anephric man. In addition, studies are proposed to document and define further the catabolic response associated with potassium deficiency.